水稻矮化卷叶基因DRL的图位克隆与作用机理研究

Leaf is the major organ for photosynthesis, research for leaf development mechanism is the basis for molecular improvement of crop plant type. The study of regulatory mechanism on the development of leaf polarity is particular in model plant Arabidopsis, However, it remains to be elucidated in monocots, especially in rice. Rice is the main staple food for a large segment of the world population. Moderate leaf rolling is an important traits of ideal plant morphology in high-yield breeding. In this study, we identified a dwarf and rolling leaf mutant drl from an ethyl methane sulfonate（EMS）mutagenesis Library of indica restorer variety Jinhui 10, which exhibited phenotypes of extremely rolled leaves during all of the stages and narrowed leaves and dwarfism which appeared during the mature stage. Histological observations indicate that drl does not form abaxial sclerenchymatous cells in a portion of small vascular bundles and replaced by mesophyll cells; the development of vascular system and the polar of adaxial-abaxial is abnormal; Abaxial surface of leaves lacking the papillaes and it can be observed at the adaxial surface. Genetic analysis showed that the drl is controlled by a single recessive gene, the DRL gene was initially localized within an interval of 95.3kb physical distance on the telomere of long arm on chromosome 3. In this study, we intend to Map-based cloning of the DRL gene and study the function and the mechanism by using molecular biology and proteomics technologies.

叶片是植物光合作用的重要器官，叶片发育机制的研究是农作物株型分子改良的基础。在拟南芥等模式植物中对叶片极性发育的基因调控机理已有较为深入的探讨，但是在单子叶植物尤其在水稻中这方面的研究还相对薄弱。水稻是我国重要的粮食作物，适度卷曲的叶片形态是水稻超高产理想株型的重要性状。本研究水稻卷叶突变体drl来源于籼型恢复系缙恢10号的EMS诱变体库。突变体drl叶片全生育期筒状卷曲至成熟期变窄，植株矮化。组织细胞学观察表明突变体叶片部分小维管束的远轴面厚壁细胞被叶肉细胞取代；维管系统发育异常；叶片的近远轴极性发育异常，叶片远轴面大瘤状乳突组织消失，而近轴面却出现了大瘤状乳突组织。遗传分析表明drl突变性状受隐性单基因控制，已将突变基因定位在第3染色体长臂端粒约95.3kb区域内，在该区域内还未见相似突变体报道。本研究拟图位克隆DRL基因，并利用分子生物学、蛋白质组学等技术研究其功能和作用机理。

卷叶作为超高产育种中理想株型的一个很重要的形态指标，对控制该性状的有关功能基因却研究得很少。在这项研究中，我们通过图位克隆鉴定了一个叶片和外稃极性发育缺陷，从而表现出叶片筒卷，外稃凹陷表型的突变体lf1。LF1基因的表达由于受到miRNA165/166的抑制，从而主要是叶片和外稃的近轴面表达。LF1基因编码一个HD-ZIP III家族的转录激活因子，定位在细胞核。LF1基因通过调控IAA的合成和信号转导过程，从而调控叶片和外稃极性的建成，进而影响叶片和外稃形态的发育。因此，本项目研究，不仅增加了人们对水稻侧生器官极性建成的遗传机制和分子调控水平的认知，同时对于遗传上控制植株的立体姿势和叶片受光形态，提高光能利用效率，同时减少叶片的蒸腾作用都具有重要意义。